Apart from varnishes for uniform colors, effect varnishes are increasingly being used for coatings, in particular for automobiles. Coatings obtained with effect varnishes exhibit differences in degree of brightness and color and differences in brilliance depending on the angle of incidence of the incoming light and the angle of observation. These phenomena are called flop effects. Such an effect with respect to brightness is obtained by using metal platelets, preferably aluminum platelets, and inorganic or organic colored pigments. In general, a two-coat design is used for this type of coating. A base coat containing the color pigment is applied to the substrate which may have been provided with a priming coat. A further coat containing the metal platelets is then applied to the base coat. Finally, this is usually followed by applying a clear coat as an additional coat.
In recent years attempts have been made to replace the metal platelets in these effect varnishes partly or completely by interference pigments, making it possible to obtain different colors depending on the angle of observation.
A pigment mixture containing an organic pigment, a nacreous pigment, aluminum particles and graphite is disclosed in EP-A-0,439,107. The desired effect is achieved by means of a one-coat system. Furthermore, a two-coat system containing a metal-free pigment in the base coat and a mica pigment and an organic pigment in the second coat, the color of the organic pigment being complementary to the color of the mica pigment, is disclosed in EP-A-0,388,932. The color of the pigment in the base coat can either be similar to the color of the organic pigment or similar to the color of the mica pigment.
German Offenlegungsschrift 3,306,400 describes coatings and surface coatings containing a platelet-shaped copper phthalocyanine pigment of the .alpha.-modification and a pigment different therefrom or a copper phthalocyanine pigment of different crystal form.
EP-A-0,455,211 describes an effect base coating for the coating of polypropylene substrates, which base coat contains an effect pigment and a color pigment, it being possible for the effect pigment to be a metal pigment or a mica-based interference pigment. The coating is applied to the substrate as a single coat. This coating is said to achieve an excellent flop effect and to make it possible for various brightness and brilliance effects to be matched.
The effect base coating described in EP-A-0,455,211 has the disadvantage that the color pigments used have a geometrical shape which is different from that of the platelet-shaped interference pigments. In general, they are approximately spherical and accordingly their sedimentation is different from that of the platelet-shaped interference pigments. This is reinforced by the different size of the particles. In general, effect pigments have a particle size of 10 to 60 .mu.m, while organic color pigments have a particle diameter of 0.01 to 0.1 .mu.m and inorganic color pigments a particle size of 0.2 to 2 .mu.m. As a result there is a risk that the mixture will separate. Moreover, the spherical color pigments are deposited on the platelet-shaped interference pigments and reduce the gloss of the interference pigment. Furthermore, a substantial expenditure is required for achieving good dispersion of the pigments in the coating system.